/*
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you under the Apache License, Version 2.0 (the
 * "License"); you may not use this file except in compliance
 * with the License.  You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing,
 * software distributed under the License is distributed on an
 * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
 * KIND, either express or implied.  See the License for the
 * specific language governing permissions and limitations
 * under the License.
 */
package org.apache.iotdb.db.utils.datastructure;

public interface QuickSort {
    /**
     * compare the timestamps in idx1 and idx2
     */
    int compare(int idx1, int idx2);

    void swap(int p, int q);

    default int partition(int lo, int hi) {
        // Choose the middle of the array as pivot.
        // In time series, usually the middle element is of middle range
        int pIndex = (lo + hi) / 2;
        // long pivot = getTime(pIndex);
        int gIndex = lo;
        // Find the greatest index not smaller than pivot.
        // while (getTime(gIndex) < pivot) {
        while (compare(gIndex, pIndex) == -1) {
            gIndex++;
        }
        for (int i = gIndex; i <= hi; i++) {
            if (compare(i, pIndex) == -1) {
                // swap the element < pivot to gIndex, and gIndex++
                swap(gIndex, i);
                // maintain the pIndex
                if (pIndex == gIndex) {
                    pIndex = i;
                }
                gIndex++;
            }
        }
        if (gIndex != pIndex) {
            swap(gIndex, pIndex);
            pIndex = gIndex;
        }
        return pIndex;
    }

    //    default void insertion_sort(int lo, int hi){
    //        for(int i = lo + 1; i <= hi; i++) {
    //        }
    //    }

    default void qsort(int lo, int hi) {
        if (lo < hi) {
            // TODO: use insertion sort in smaller array
            // if(hi - lo <= 32) {
            //    insertion_sort(lo, hi);
            // }
            // partition
            int pivotIndex = partition(lo, hi);
            qsort(lo, pivotIndex - 1);
            qsort(pivotIndex + 1, hi);
        }
    }
}
